|Poster for Twilight Breaking Dawn Part 2|
Speaking on the red carpet outside the Odeon cinema in Leicester Square, Kristen, 22, told BANG Showbiz: "[Mackenzie's] like one of the coolest kids I've ever met. She use to always be like, 'I want to be a movie director!'
"I think every single member of the cast was like, 'Cool! Call me for a job because I will work for you'. She's amazing."
Robert's comment echoed his real-life girlfriend Kristen's, adding that working with Mackenzie made the filming "spontaneous".
He said: "I like working with kids - it's really easy. Kids do all the work for you! Everyone's got their focus on the baby and Mackenzie.
"Mackenzie's a great actress. It just makes it really easy, everything's spontaneous."
Both stars, along with 20-year-old Taylor Lautner who plays werewolf Jacob Black in the films, were greeted by a crowd of around 6,000 'Twihard' fans who had gathered in the cold to get a glimpse of their idols.
Although Robert may have wanted to stay and party after the event, when asked what his plans were later that evening he laughed and replied: "I have to go out to Madrid to do the next premiere!"